Boston has excellent seafood from the nearby New England coast. Local specialties include baked beans, cod, lobster rolls, and clam chowder. For dessert you'll have no trouble finding good ice cream. Boston are one of the top per-capita ice cream consuming regions.
A variety of excellent ethnic restaurants can be found in neighborhoods such as the North End, Chinatown, Allston, or Coolidge Corner.
The best sit-down restaurants can be quite crowded in the evenings on weekends. Unless you have a reservation, be prepared to wait anywhere from a few minutes to an hour, depending on how refined your tastes are.
The North End is full of Italian eateries, and it's certain that you'll find something here to your liking. Take the Green or Orange Lines to the Haymarket station, cross the Greenway park(what used to be Interstate 93 pre-Big Dig), and then follow the signs to Hanover Street, the main commercial thoroughfare. Most of the good restaurants are on this street or on side streets. If you visit the North End on the weekend in the summer you may encounter one of many saint's festivals. Streets are closed off and there are music, food, and parades of the saint's statues.
The Bull & Finch Pub in Beacon Hill was the inspiration for the hit television show "Cheers." Very pricey for bar fare, but an essential part of the Boston tourist experience. The Beacon Street address is the original and does not look much like the set of the show. There is another Cheers at Faneuil Hall which is more of a replica of the TV set. If you ask a local for directions to Cheers, you may be directed to Faneuil Hall. The Beacon Street bar is referred to by its original name. Both locations are very touristy complete with souvenir shops.
Legal Sea Foods is a Boston original - well, technically Cambridge, since it started as a fish market in Inman Square, Cambridge. Legal Seafood is known for its New England Clam Chowder. Expect to pay between $25–30/person at dinner at one of their multiple locations.
Despite having a huge student population, the political clout of residential neighborhood associations who value late-night peace and quiet has historically kept Boston from offering many options for late-night dining. Most restaurants close by 10 or 11PM, even in college neighborhoods such as Allston and Brookline. Bars stay open till 2AM for drinking but their kitchens usually close at midnight or earlier. Exceptions are found in Chinatown, where several eateries serve their full menu till 2AM or later, and in the South End, where dining until midnight is possible even early in the week. If you're planning a long night, though, it's probably best to plan ahead and buy some snacks in advance.